The present invention relates to a process for the production of solvent-refined coal which comprises heating the coal whilst slurried in a solvent under hydrogenation conditions to substantially liquefy the coal, followed by a step of separating the non-dissolved solids from the solution which is formed as a result of said liquefying.
In the so-called solvent refining of coal, which process can be applied to moderately high rank through to low rank coals, the coal, in a particulate condition is subjected to liquefaction in a high-boiling solvent (e.g. boiling between 200.degree. and 450.degree. C.), suitable as a hydrogen carrier (in a physical and/or chemical sense) at a temperature above 350.degree. C., say between 350.degree. and 500.degree. C. in the presence of hydrogen at a pressure of about 30 to 250 bar. After having been subjected to this treatment for about 15 for 120 minutes, more particularly 50 to 90 minutes, the pressure is let down from the reaction product and the liqueform reaction mixture is subjected to a step of solids separation, usually filtration, in order to remove therefrom all non-dissolved matter, namely the char-like solid such as fusain and the ash. The clear liquid phase is then subjected to distillation whereby the solvent is recovered and recycled, whereas the substantially non-volatile bottoms of the distillation constitute the so-called solvent refined coal (SRC) which can serve as a feed stock for catalytic hydro-cracking.
The solvent-refined coal can also be put to a number of other uses. It may be used as a fuel per se or in blends. In appropriate circumstances it can also be used as a feedstock for processing to fuels or petrochemicals and their precursors. Suitable forms of solvent-refined coal (also known as SRC) may be used as a constituent of coking coal blends or for the manufacture of carbon electrodes.
The step of separating the non-dissolved solids from the resulting solution, usually carried out by filtering, has in the past been a source of technical difficulties contributing to high production costs. Largely as a result thereof, the manufacture of SRC has up till now not been commercially attractive, and work on the production of SRC had been substantially confined to laboratory work and experiments on a smaller than normal production scale. The terms "SRC" or "solvent-refined coal", both in relation to the product and to the process of making such product, have acquired a distinct meaning in the art, which meaning is to be distinguished from different processes which are more correctly described as destructive hydrogenation or hydrogenative cracking and which result predominantly in liquid and/or gaseous products.